Process of bleaching soap stock



Patented Dec. 6, 1932 UNITED STATES PATENT OFFICE ANTHONY M. LAGASSE, OF ARLINGTON, NEW JERSEY, ASSIGNOR TO STOCKTON G. TURNBULL, OF ARLINGTON, NEW JERSEY PROCESS OF BLEACHING SOAP STOCK No Drawing.

This invention relates to a process of bleaching soap stock and of making soap and more particularly to the bleaching of low grade greases and tallows or discolored soap stocks with hydrogen peroxide to form a stock that may be made into a white or light colored soap of the density and other properties required for commercial soap.

When a soap stock is bleached with hydrogen peroxide in the processes heretofore known, a number of disadvantages and defects are encountered that render the resulting product unsuited for commercial soap making. Among these disadvantages is the tendency of the resulting stock to become very highly porous when made into a soap, the resulting soap being of a very light, foamy structure filled with minute voids so that its density is but a small fraction of that required for a commercial soap, even one of the floating type. This extreme. porosity cannot be removed in the soap making steps of closing out nor in any of the known soap making operations, but persists throughout these operations and remains in the final product. As a result, the product cannot be formed into a soap of the required hardness, firmness or density.

Other disadvantages of the bleaching of soap stocks with hydrogen peroxide in the processes heretofore known are the tendency of the resulting soap to revert in spots when stored and to take on a discolored appearance, and the excessive amounts of hydrogen per- 3 oxide required in the bleaching, which raises theecost of the resulting product to such an extent as to counteract the advantages of using cheap, low grade or discolored stocks.

An object of my invention is to obviate 4 these disadvantages and to provide a process in which low grade tallows. greases or soap stocks may be bleached with hydrogen peroxide in such a manner as to produce a soap of commercially usable density and consistency, or to produce a stock that may be made into a soap of commercial properties.

Other objects of the invention are to provide a process of bleaching low grade, discolored soap stocks by means of hydrogen peroxide in Which the quantity of hydrogen Application filed May 31,

peroxide required for effective bleaching is greatly reduced, in Which the subsequent soap making steps are simplified and easier to carry on, and in which a permanent nonreversible bleaching is obtained.

Other objects of the invention Will be apparent from the detailed description in the following specification.

In bleaching a low grade, discolored grease or soap stock by my invention the stock is preferably filtered through a filtering earth and decolorizing carbon to remove those impurities that may be filtered or adsorbed out of the stock. The filtered soap stock is then emulsified in an acid or non-alkaline condition with a solution of hydrogen peroxide, the quantity of hydrogen peroxide (H 0 in solution being not more than about 1% of the Weight of the stock. The resulting emulsion is agitated for a sufiicient time to enable the hydrogen peroxide to completely bleach the soap stock or to bleach it to the desired extent. The length of time for this bleaching will depend to some extent upon the fineness of the emulsion. When the bleaching action is completed the agitation of the emulsion is continued at an elevated temperature for a sufficient time to cause all of the hydrogen peroxide to completely decompose, it being important that no hydrogen peroxide should 8 remain in the stock when it is subjected to the soap making operations. as it causes foaming and porosity in an alkaline solution.

An example of bleaching a soap stock in accordance with my invention is as follows: 2500 parts by weight of house grease is heat-' ed to 105 C. and treated with from 50-100 parts by weight of a mixture of equal parts of decolorizing or filtering carbon and of acid treated earth. This mixture is disseminated throughout the soap stock and is allowed to settle downwardly through it. The time of settling will depend, to some extent, on the depth of the body of soap stock. During this period of settling tlic temperature of the stock should be maintained at about 105 C. The molten stock is then filtered and is ready to be bleached. The filtered stock is then brought to 45 C. in a hard glass, porcelain, aluminum or enamel container and is then treated with a, solution of hydrogen peroxide. Iron containers are unsuitable at this stage as iron or iron rust decomposes the hydrogen peroxide very rapidly with an appreciable loss of oxygen.' Then from 1 to 1 parts of hydrogen peroxide solution per 100. parts by weight of the stock are added to the stock with constant stirring so as to form an emulsion with the stock. In general, a quantity exceeding 1% of the weight of the stock is sufficient.

The concentration of the hydrogen peroxide may be varied provided the proportion of the peroxide is not increased or diminished. It isadvantageous to use no more of the hydrogen peroxide than is required to accom- -plish the bleaching of the soap stock, as the excess must be removed before the stock is saponified in the subsequent soap making operation.

It is of importance to very thoroughly agitate the hydrogen peroxide solution with the soap stock so as to form a good emulsion of the hydrogen peroxide solution in the-stock. This agitation is maintained for about ten to fifteen hours at from to C. The time of a itation may Vary with different types of greases or stocks. If the agitation is not sufliciently maintained, the emulsion has a tendency to break, thereby resulting in a poor contact between the hydrogen peroxide and the grease and, consequently, the peroxide decomposes without accomplishing the desired bleaching effect. The time for complete reaction between the hydrogen peroxide and the grease or soap stock is shorter the more perfect the emulsion,- which permits a higher temperature to be employed without a corresponding loss of oxygen from the bleaching reaction.

The soap stock and hydrogen peroxide must be permitted to remain in a non-alkaline or acid condition until the hydrogen peroxide is completely decomposed or is sufiiciently decomposed so that in the subsequent soap making operations the soap stock will not be formed into a froth or foam by the dispersion therein or in the resulting soap of permanently enclosed voids or bubbles of air. The extent of the decomposition may be controlled by testing aselected sample of the stock in the soap making operation and determining whether it foams when subjected to saponifying and soap making operations.

When the soap. stock is made into soap up to 2% of its weight of borax, water glass or other mildly alkaline or organic filler may be added to improve the consistency of the resulting soap.

The soap stock may then be made into a soap by any of the usual soap making operations.

In testing the soap, the saponification number of the stock is determined and from of hydrogen peroxide (H O) not this the quantity of caustic soda to neutralize 100 grams of grease. The stock is then saponified with about 5% excess of caustic soda. If the peroxidation is complete and the hydrogen peroxide has been completely decomposed, there should be no foaming or frothing of the stock when the caustic is added. The liberation of oxygen in the form of foam on saponifying the stock will indicate that the temperature during the peroxidation operation was not high enough to decompose completely the hydrogen peroxide not consumed in the bleaching or that the time of bleaching was not long enough.

The presence of any-unrcacted hydrogen peroxide at the time of saponification is of no benefit but, on the contrary, is a disadvantage and presents difliculties in saponification owing to the formation of a thick layer of froth which tends to expand suddenly and overflow the soap pan. It also materially retards saponification. The caustic acts as a violent decomposing agent and dissipates the peroxide very rapidly. If the hydrogen peroxide has entirely reacted in the bleaching step there is no substantial foaming and the saponificatlon will proceed smoothly.

A specific example of a test is as follows: The bleached grease is melted and the NaOI-I is added a little at a time. It is important that the caustic be added a little at a time at the beginning, because too much caustic gives rise to the formation of granules which are quite difiicult to break up and take up more time for the saponification to be completed. If just enough caustic. is added to form a homogeneous paste when agitated and heated, the saponification will proceed very smoothly. The temperature is raised until the mass just boils and the full amount of caustic is slowly added with occasional. agitation, over a period of four to five hours. A convenient temperature is about 100 C. to 110 C. for the first hour, with a gradual increase to 130 C. to 140 C. until there is a vigorous boil and the saponification is complete. 'It will be necessary to Watch this very closely after the first hour, as the volume of the mass will expand to two or three times its natural depth and will often overflow. Then the temperature can be lowered slightly, just 1 sufficiently to allow' a continuous boil described best by a continuous rolling and overlapping of folds of the homogeneous paste, like turbulent waters flowing toward the center of the surface of the mass.

If the bleaching with hydrogen peroxide has been completely carried out and the hydrogen peroxide dissipated, the above saponificatlon step and any of the subsequent steps of closing out or salting out may be readily carried on without foaming." However, if the stock still contains hydrogen peroxide, this will be indicated by the foaming-of-the stock during saponification and the persistence of a porous or foaming condition throughout the soap making operations and in the final product. This may be corrected by the continued decomposition of the hydrogen peroxide before saponification until a test sample indicates dissipation or decomposition of the hydrogen peroxide remaining after the bleaching operation.

It will be understood that the quantities employed and the conditions of bleaching may be modified to suit difi'erent stocks. The step of peroxidation and the subsequent re moval of hydrogen peroxide should be done in a neutral or slightly acid condition and avoiding any alkalinity in the presence of the hydrogen peroxide.

Under the above conditions the bleaching may be accomplished with a minimum of hydrogen peroxide, the quantity of 100% H O being not greater than 1% of the weight of the grease or stock to be bleached.

It will be understood that the quantity of hydrogen peroxide solution will be larger,

the lower the concentration of the hydrogen peroxide so as to maintain the required quantity of peroxide.

What I claim is:

1. The process of bleaching soap stock which comprises treating said soap stock with hydrogen peroxide in non-alkaline condition, and decomposin .the excess hydrogen peroxide after the bleaching operation is completed.

2. The process of bleaching soap stock which comprises treating said soap stock with hydrogen peroxide in slightly acid condition, and decomposing the excess hydrogen peroxide after the bleaching operation is completed.

3. The process. of bleaching soap stock which comprises emulsifying said soap stock with a solution of hydrogen peroxide 1n nonalkaline condition, maintaining the temperature'at 35 to 55 C. and decomposing the excess of hydrogen peroxide after. the bleaching is completed. 4. The process of bleaching soap stock which comprises treating said soap stock with filtering materials, removing said filtering materials, emulsifying said stock with a solution of hydrogen peroxide in non-alkaline condition, and decomposing the excess of hy-.

drogen peroxide after the bleaching is completed.

5. The process of bleaching soap stock which comprises treating said soap stock with filteringearths and, carbons, removing said filtering earths and carbons, emulsifying bon, removing said acid treated earth and decolorizing carbon, emulsifying said vstock with a solution of hydrogen peroxide in nonalkaline condition, and decomposing the excess of hydrogen peroxide after the bleaching is completed.

7 A process of bleaching soap stock which comprises treating said stock with not more than. 3.3 of its weight of 30% hydrogen peroxide in a non-alkaline condition, and decomposing the excess of hydrogen peroxidehand.

ANTHONY M. LAGASSE. 

